1. Field of the Invention
The present invention relates to a semiconductor device and its manufacturing method, a circuit board, an electro-optic device and an electronic device.
Priority is claimed on Japanese Patent Application No. 2004-313839, filed Oct. 28, 2004, the content of which is incorporated herein by reference.
2. Description of Related Art
In circuit boards and liquid crystal displays which are used in various kinds of electric devices, semiconductor devices such as integrated circuit chips (IC chips) are mounted on the boards. For example, in a liquid crystal display, an IC chip for activating a liquid crystal panel is mounted on a glass board (the partner board) which is a component of the liquid crystal panel (a so-called COG structure). In a case in which an IC chip made of hard silicon board is mounted on a hard glass board, it is hard to absorb warpage of the IC chip and the glass board. To solve this problem, bump electrodes are formed on the IC chip, and the IC chip is mounted on the glass board by compressing the bump electrodes. This process enables the IC chip and the glass board to be conductively connected.
Recently, terminals of IC chips are increasing in accordance with the high-definition of liquid crystal displays, and at the same time, downsizing of IC chips is eagerly demanded. To achieve this, narrowed pitches between bump electrodes formed on an IC chip are needed. Because an ordinary bump electrode is formed by carrying out electrolytic Au plating on an aperture of a plating resist, enlargement of the aspect ratio of the aperture is needed to narrow pitches between bump electrodes. Therefore, it is difficult to narrow pitches between bump electrodes.
A resin bump electrode 10 shown in FIG. 8 has been developed. The resin bump electrode 10 is made by forming a conducting layer 20 on a resin bump 12, and the conducting layer 20 is connected to an electrode pad 24 of an IC chip 21 (for example, refer to Japanese Unexamined Patent Application, First Publication No. H01-13734). The resin bump electrode 10 makes elastic deformation by contacting a partner board, and the warpage of the IC chip 21 and the partner board can be absorbed. Since this process does not require enlargement of the aspect ratio of the aperture, it is easier to narrow pitches between bump electrodes than in an ordinary method.
However, because the resin bump 12 has high coefficient of thermal expansion, when carrying out a hot press bond of the IC chip 21 and the partner board, the conductive layer 20 receives great tensile stress due to deforming following the expansion of the resin bump 12.
There are some cases in which sufficient reliability in the conductive connection is not obtained because of a breaking of the conductive layer 20 by the deformation of the resin bump 12 which deforms due to absorbing the pressure of the bonding.